Corneal biomechanical properties distribution in myopic population

AIM: To evaluate distribution of corneal biomechanical measurements in normal myopia and myopic-astigmatism population.<p>METHODS:One hundred and eighty eyes with myopia and myopic-astigmatism candidated for laser refractive surgery were included in this study. Complete examination of anterior and posterior segments, manifest refraction spherical equivalent(MRSE), Orbscan and Zywave were performed preoperatively. Ocular response analyzer(ORA)was used to measure corneal hysteresis(CH), corneal resistance factor(CRF), Goldmann-correlated intraocular pressure(IOPg)and corneal compensated IOP(IOPcc). Distribution of all corneal biomechanical properties and correlation between these parameters and MRSE, age and sex were determined. Statistical analysis was performed using SPSS 17 software and a <i>P</i>-Value less than 0.05 was considered significant. <p>RESULTS: Mean age was 28.20±6.78 years. Mean MRSE was -4.21±1.19D. Mean CH, CRF, IOPg and IOPcc was 10.00±1.28mmHg, 10.17±1.45mmHg, 15.71±2.67mmHg and 16.68±2.41mmHg respectively. 28.4% of all myopic population had CH about 10mmHg, and 71% had CH, 9mmHg up to 11mmHg. CRF in 25.9% of myopic population was 10mmHg, and in 48.7% was 9mmHg up to 11mmHg. There was very poor positive correlation between MRSE& CH(Rs=0.001, <i>P</i>=0.71)and MRSE& CRF(Rs=0.01, <i>P</i>=0.18).<p>CONCLUSION: Our study demonstrated the distribution of corneal biomechanical properties(CH, CRF, IOPg, IOPcc)in normal myopia and myopic-astigmatism population in Iran, and confirmed that, there was no statistically significant correlation between CH, CRF and MRSE, age and sex but there was significant correlation between IOPg, IOPcc and formerly mentioned parameters

A Comprehensive Review of DC-DC Converters for EV Applications

DC-DC converters in Electric vehicles (EVs) have the role of interfacing power sources to the DC-link and the DC-link to the required voltage levels for usage of different systems in EVs like DC drive, electric traction, entertainment, safety and etc. Improvement of gain and performance in these converters has a huge impact on the overall performance and future of EVs. So, different configurations have been suggested by many researches. In this paper, bidirectional DC-DC converters (BDCs) are divided into four categories as isolated-soft, isolated-hard, non-isolated-soft and non-isolated-hard depending on the isolation and type of switching. Moreover, the control strategies, comparative factors, selection for a specific application and recent trends are reviewed completely. As a matter of fact, over than 200 papers have been categorized and considered to help the researchers who work on BDCs for EV application

Analysis and Design of a Soft Switching Z-Source Boost DC-DC Converter

This paper proposes a high step-up fully soft switched Z-source Boost DC-DC converter, which uses two resonant paths to create soft switching conditions for switches and diodes and also increases the voltage gain. The proposed converter only has one switch, so it has a simple structure. Furthermore, its control circuit remains pulse width modulation. Since soft switching conditions are provided for all switching elements, the converter efficiency is very high. This converter also has all advantages of Z-source converters. The converter is analyzed and simulated in PSPICE software. The results confirm the aforementioned advantages and features of the proposed converte

Hospital Patient Safety Culture in Developing Countries: A Comparative Study in Ilam City, Iran.

Aims: In this study, patient safety culture was assessed in four educational hospitals in Ilam city, Iran. Study Design and Setting: A cross-sectional study was carried out in four educational hospitals (Imam Khomeini, Mustafa Khomeini, Taleghani and Kowsar hospitals) in Ilam city (Iran). Study Duration: The study was conducted over 2014. Methods: The data collection was conducted via the Iranian version of Hospital Survey on Patient Safety Culture (HSOPSC) questionnaire. The questionnaire contains 42 items that evaluates 12 dimensions of patient safety culture. Results: The results showed that 47% of the participants had 1- 5 years of work experience and 71.1% of them worked more than 40 hours per week in hospital. The mean positive answers score of the safety culture in this study was obtained 40% that was much lower than the benchmark (64%). The highest and lowest percentages of the positive answer were attributed to teamwork within units (70%) and non-punitive response to error (11%), respectively. Conclusion: In order to increase the patient safety culture in the hospitals, the number of professional staff should be increased and a practical plan about the patient safety culture should be provided. Moreover, the hospitals management should support the staff to report errors without fear of the punishment

Corneal collagen cross-linking effects on pseudophakic bullous keratopathy

AIM: To evaluate the efficacy of riboflavin administration and ultraviolet A(UVA)cross-linking on advanced symptomatic bullous keratopathy. <p>METHODS: Fifteen patients with symptomatic pseudophakic bullous keratopathy(PBK)were included. Slit-lamp examination, visual acuity, foreign body sensation(FBS)questionnaire, corneal clarity grading, ocular pain intensity scale and corneal thickness measures with Pentacam and ultrasound pachymetry(UP), were performed before corneal cross-linking and 1 and 6mo thereafter. After using sodium chloride solution, for one week, the central 8mm(diameter)of the corneal epithelium was removed, and cross-linking, with riboflavin instillation every 3min for 30min, and UVA irradiation for 30min was performed. <p>RESULTS: Five males and 10 females with mean age of 66±13y were included. Mean follow up time was 6.2mo. Corneal transparency in all eyes was statistically significantly better 1 month after treatment than preoperatively(<i>P</i><0.05). At 6mo, however, corneal transparency was better in 8 eyes, the same in 5 eyes, and worse in 2 eyes compared with preoperative levels(<i>P</i>= 0.218). Foreign body sensation subsided in 70% of patients. The average CCT decreased within 1mo after the procedure(<i>P</i><0.05). At 6mo, all but 3 eyes had progressive swelling, and the CCT increased; however, the CCT was still statistically significantly thinner than preoperatively(<i>P</i>=0.006). The improvement in mean CDVA from preoperatively to 1mo postoperatively was statistically significant(<i>P</i>=0.010). At 6mo, no significant differences were observed(<i>P</i>=0.130). The pain scores at 1mo were statistically significantly better than preoperatively(<i>P</i>=0.007). At 6mo, however the mean pain score was higher than at 1mo and not statistically significantly different from the preoperative score(<i>P</i>=0.070). <p>CONCLUSION: Corneal CXL significantly improved corneal transparency, corneal thickness, and ocular pain 1 month postoperatively. However, it did not seem to have a long-lasting effect in decreasing pain and maintaining corneal transparency in patients with PBK. This procedure extends the time interval for corneal transplantation and increases visualization at DSAEK procedure

Managing New PV Plant Connection to Available Grids to Stay within Standard Limits with a Case Study

PV plants are increasing all over the world and they are becoming a distinct part of electric grids. Due to abundance of solar irradiation and almost constant amount of it in certain geographical latitudes, selection of proper capacity of PV plants depends mostly on available places for the site. In this paper, important measures for safe connection of a PV plant in terms of voltage requirements are addressed and several guidelines are introduced for this purpose. In addition, simulation results are included to prove some of the mentioned suggestions. A general algorithm is finally proposed to show the directions for safe connection of PV plants

A Novel Hybrid Framework for Co-Optimization of Power and Natural Gas Networks Integrated With Emerging Technologies

In a power system with high penetration of renewable power sources, gas-fired units can be considered as a back-up option to improve the balance between generation and consumption in short-term scheduling. Therefore, closer coordination between power and natural gas systems is anticipated. This article presents a novel hybrid information gap decision theory (IGDT)-stochastic cooptimization problem for integrating electricity and natural gas networks to minimize total operation cost with the penetration of wind energy. The proposed model considers not only the uncertainties regarding electrical load demand and wind power output, but also the uncertainties of gas load demands for the residential consumers. The uncertainties of electric load and wind power are handled through a scenario-based approach, and residential gas load uncertainty is handled via IGDT approach with no need for the probability density function. The introduced hybrid model enables the system operator to consider the advantages of both approaches simultaneously. The impact of gas load uncertainty associated with the residential consumers is more significant on the power dispatch of gas-fired plants and power system operation cost since residential gas load demands are prior than gas load demands of gas-fired units. The proposed framework is a bilevel problem that can be reduced to a one-level problem. Also, it can be solved by the implementation of a simple concept without the need for Karush–Kuhn–Tucker conditions. Moreover, emerging flexible energy sources such as the power to gas technology and demand response program are considered in the proposed model for increasing the wind power dispatch, decreasing the total operation cost of the integrated network as well as reducing the effect of system uncertainties on the total operating cost. Numerical results indicate the applicability and effectiveness of the proposed model under different working conditions

An Optimized Multi-Layer Resource Management in Mobile Edge Computing Networks: A Joint Computation Offloading and Caching Solution

Nowadays, data caching is being used as a high-speed data storage layer in mobile edge computing networks employing flow control methodologies at an exponential rate. This study shows how to discover the best architecture for backhaul networks with caching capability using a distributed offloading technique. This article used a continuous power flow analysis to achieve the optimum load constraints, wherein the power of macro base stations with various caching capacities is supplied by either an intelligent grid network or renewable energy systems. This work proposes ubiquitous connectivity between users at the cell edge and offloading the macro cells so as to provide features the macro cell itself cannot cope with, such as extreme changes in the required user data rate and energy efficiency. The offloading framework is then reformed into a neural weighted framework that considers convergence and Lyapunov instability requirements of mobile-edge computing under Karush Kuhn Tucker optimization restrictions in order to get accurate solutions. The cell-layer performance is analyzed in the boundary and in the center point of the cells. The analytical and simulation results show that the suggested method outperforms other energy-saving techniques. Also, compared to other solutions studied in the literature, the proposed approach shows a two to three times increase in both the throughput of the cell edge users and the aggregate throughput per cluster

Analysis and design of a high efficiency bidirectional DC-DC converter for battery and ultracapacitor applications

This paper presents a high efficiency non-isolated bidirectional converter which can be employed as an interface circuit between ultracapacitors or batteries and DC bus voltage. All semiconductor devices in the proposed converter are soft switched while the control circuit remains PWM. So, the energy conversion through the converter is highly efficient. The proposed converter acts as a zero-voltage transition (ZVT) buck to charge an ultracapacitor or battery and acts as a ZVT boost to discharge an ultracapacitor or battery. The performance of the proposed converter with respect to abrupt load and operating mode change is shown through computer simulation results. The results confirm the aforementioned advantages and features of the proposed converter

Day-Ahead Network-Constrained Scheduling of CHP and Wind Based Energy Systems Integrated with Hydrogen Storage Technology

The integration of renewable energy sources is vastly increased in recent decades considering environmental concerns and lack of fossil fuels. Such integration has appeared novel challenges in electrical energy systems according to their uncertain nature. The hydrogen energy storage (HES) system plays a significant role is power systems by converting extra wind power to the hydrogen using power to hydrogen (P2H) technology. In addition, the emerging technologies such as combined heat and power (CHP) units are effective in increasing the efficiency of power systems. This work presents a day-ahead scheduling scheme for CHP-HES based electrical energy networks with high integration of wind power sources. The effectiveness of the presented model is investigated by implementation on the IEEE 6-bus system. The impact of heat load increment has been studied on scheduling of generation plants, wind power dispatch and operation cost of the system. The simulation results prove that operation cost of the system and wind power curtailment have been decreased using the HES technology